Glass.



UNITED sTArrE s PATENT OFFICE.

EUGENE C. SULLIVAN AND WILLIAM C. TAYLOR, OF CORNING, NEW YORK,ASSIGNORS T0 CORNING GLASS WORKS, OF CORNING, NEW YORK, A CORPORATION OFNEW YORK.

GLASS.

Specification 01 Letters Patent.

Patented May 27, 1919.

No Drawing. Original application filed June 24, 1915, Serial No. 36,136.Divided and this application filed September 18, 1916. Serial No.120,758,.

To all whom it may concern:

Be it known that we, EUGENE C. SULLIVAN and lViLLiAM C. TAYLOR, bothcitizens of the United States of America, and residents'of Corning, NewYork, have invented certain new and useful Improvements in Glasses, ofwhich the following is a specification.

In our prior application filed June 24, 1915, Sr..No. 36,130, we showed,described and claimed a glass baking dish and compositions for a glasssuitable for fabrication into such dishes. The United States PatentOflice has required a division of such application between the claims onthe article and those on the composition and accordingly the presentapplication is filed. Glass compositions A, B C, D and E given hereinare compositions iven. in the prior application. Composition fi givenherein is specified because it is a composition which has been put intoextensive commercial use and because its physical properties have beencarefully and accurately determined.

Our invention has for its object to provide a new glass (that is to saya substance containing silica in combination with various bases andacids) especially adapted for fabrication into pressed or blown wareintended for culinary or laboratory uses. For these purposes it isdesirable that the glass have the following properties.

(A) A high co-efiicient of thermal endure ance, as hereinafter defined.

(B) High stability, that is to say, power to resist chemical attack. f

It is well known that certain glass making materials tend, whenincorporated in the glass, to produce one or more of the desirableresults, but in so doing, many of them also work against other desirableresults, and in advance of an actual test, it cannot be predicted how avariation of the relative proportions of the diiferent. ingredients willaffect certain of the named factors. This invention therefore consistsin the selection of certain known glass making materials in.

Generally speaking, the present invention contemplates a glass for thepurposes stated, characterized by one or more of the following features,

(1) It is boro-silicate of high stability having a linear co-efficientof expansion less than .000004 and a high thermal conductivity e. ashigh as .0028).

(2) In it the molecular ratio of silica to base is greater than 13 to 1,(tending to high stability (resistance to attack of reagents) and lowexpansivity), while at the same tim its hardness (as measured in themanner hereinafter stated) is less than 900.

(3) In it the molecular ratio of acid oxid or oxids to basic oxid oroxids is not less than 15 to 1. Y

(4.) It has a co-eflicient of thermal endurance greater than 6.

(5) It has a stability better than .002 grams per 100 sq. cm. whenmeasured in the manner hereinafter stated.

It more specifically comprises a boro-silicate glass, in which no oxitlsof the second group of the eriodic system are present in quantities sucient to make "them material constituents, containing over 75 per cent.of

silica, and having a hardness of about As examples of glass compositionsfalling within our invention, we give the follow- A. B B D. SiO 70 80. 680. 9 90 85 90 B203 20 13 12. 9 6 12. 5 5 Na O 4 4 4 4. 4 1. 5 A1 O 6 1.8 $11203 1 L120 Total- 100 100 100 100 100 100 All of the glasses givenabove have the following physical characteristics,-

(1) A linear thermal expansivity less than .000004, between 20 C. and300 0., the co-efiicient of expansion of glass (A) being. 0000037; of B,.0000034; of B, .0000033; of 0., .0000023, and of D, .0000022.

(2) A. relatively hi h co-eificient of true internal heat conductively,viz., .0028 calories per second per degree C. for each square centimeterof plate 1 cm. thick, for glasses A, B, and B and about .0030 for C.

(3) Tenacity, modulus of elasticity density and specific heat of suchvalues that in connection with their ,expa'nsivity and conductivity theglasses have a high co-eflicient of thermal endurance. This factor,which is the power to undergo sudden cooling without fracture, isexpressed by Winkelmann and Schott (Ann. d. Phys. u. Chem. 51-730(1894); also Hovestadt, Jena Glass, published by MacMillan 1902, p.228), as

follows 7 inds? V in which Fzco-eflicient of thermal endurance,Pztensile strength,

a the linear expansivity, EzYoungs modulus of elasticity, K=heatconductivity,

S density,

czspeeific heat.

If the cubic expansivity is used in the formula, instead of the linearexpansivity the result would be and these values of are used forcomparing glasses. The values of gcalculated by Winkelmann and Schottfor glasses of various composition range between 1.17 and 484:.

' In calculating gwinkelmann and Schott use a figure forthe tensilestrength which is undoubtedlytoo low, their tensile strengthdetermination having been made by a method which they themselvesrecognized tended to give low results.

Using factors of tensile strength for our glasses, such as would begiven by them under the test methods of Winkelmann and Schott, the.cubic co-,efiicient of thermal endurance ),of all of our. glass isgreater than 6. In specifying thermal endurance in our-claims, we willbase them on such factors. Using the actual tensile strength of ourlasses the factor is still higher.

'(4 High stability against chemicalattack.. As illustrative of this, itmay be stated that a' las of composition B after bein subjects to thesolvent action of distill water at 80 C. for 48 hours (see forpr0eedure,-Walker, Jo'wmal of the America/n Chemical Society, vol. 27 p.865, 1905) has only .0001 to .0005 grams of matter dissolved per 100 sq.em. exposed to the solvent action,

while all of the compositions here given have a stability better-than.002 grams per 100 (5) Good workability This includes-the ability toproperly melt the lass at the ternperatures readily .ob ta.inab eordinary tent.

glass furnaces. It also includes the property of remaining amorphous,and of being sufficiently plastic at a point below the furnacetemperature to permit its Working in the ordinary manner by blowing,pressing, etc.

This latter property may be expressed numercially by the temperature onthe centigrade scale, at which a thread of the glass 1 mm. in diameterand 23 cm. in length sus- Chemically, the compositions above given areeharacterized,-- (7) By high silica contents (5. e. not less than 70%).This tends to.low expansivity and good stability, but tends to renderthe glass hard.

It will be noted that in all of the above I formulae the percentage ofalumina is very low, as is desirable in order to reduce the hardness ofthe glass. Alumina has been heretofore used in sodium-boro-silicateglasses in larger percentages in order to obprevent crystallization, butwe find it possible to still achieve these desirable results whilereducing the alumina contents, and to increase as stated, in a suitablemixture, the

.tain ability to resist chemical attack and p silica contents to 70 percent. or over, and

that the; expansion with such percentages is less than would be inferredfrom the hitherto known properties of silica. From our investigations wehave discovered that with these high percentages of silica, the unitexpansion factor of the silica is apparently less than the unit factorfor less percentages of silica, or in other words that when thepercentage of silica is made sufliciently great the factor by whi ch itspercentage is to be multiplied to obtain the thermal expansion due tothe silicais reduced. Ifthe silica content is increased to above 84 percent., which is thus rendered possible, while maintaining low expansion,the alumina contents may be decreased, say to one per cent., owing tothe fact that with high silica contents suitably combined, but littlealumina is required to give requisite resistance to chemical attack,and. freedom from tendency to crystallize. In composition D, theantimony, and composition 'E, the lithia, serves to soften the glasswithout decreasing the resistanceto chemical atv I tack as would theamount of soda or potash soften the glass to'thesam'e exrequisite toIndeed the alumina of compositions A, B B G and E may be entirelydropped, being replaced by an equal amount of silica. This, whileeffecting changes in the characteristics of the glass, is within thescope of certain aspects of our invention and the resultant glasses areuseful, although not embodying desirable features to the same eX- tentas the compositions given. Thus if this change be made in composition13,, the re sultant glass would be lower in expansivity, softer, lessstable and more inclined to crystallize than the glass of composition B(8) In combining with the low eXpan-' sivity due to the high silicacontents, and with good stability, good workability, this being due tothe compositions employed, in which a relatively high ratio of boricoxid to alkali, is present, this ratio in none of, the cases given,being less than 2 to 1, the boric oxid (except for compositions E) beingbetween 60 and 70 per cent. of constituents other than the silica. It ispossible to replace a part of the sodium oxid given in the formulae withpotassium oxid. To obtain the same hardness, two parts of sodium oxidmay be replaced by three parts of potassium oxid, while for the sameexpansivity, five parts of sodium oxid may be replaced by six parts ofpotassium oxid.

.In this specification, the proportions of alkali Will be stated interms of sodium oxid, it being understood that such alkali may-bereplacedby potassium oxid in the proportions stated. It will be noted inglass 'E, lithia forms the alkali.

four ingredients each, at least two of which are acid oXids (silica andboric oXids), and a basic oxid (soda or lithia). Alumina and theantimony oxid probably act as acids in the composition, and will forpurposes of description be so considered. This simplicity of compositionis of advantage in connection with chemical glass-ware by reducing thenumber of elements which'may be taken up from the glass by substancesundergoing analysis or treatment therein.

It will be noted that in the compositions given, themolecular ratios ofsilica to bases and of acidic oxids to basic oXids are high. The firstratio for A is 18 to 1; for B, 18.9 to 1; for 13,, 19 to 1; for C, 31 to1; for D, 51 to 1; and for E, 15 to 1 while the second ratio for A, is23 to 1; for 13,, 21.4 to 1; for B 21.6 to 1; for C, 33 to 1; for D, 58to 1; for E, 15.7 to 1; the molecular formulas of the severalcompositions being as follows,

B1. B2. c. D. E. 1.345 1. 348 1.5 1.417 1.5

It will be noted that none of the oxids of the second roup of theperiodic system (c. g. lime an magnesia) are present, for while theseoxids tend to stability and good workability, they also tend to producein such compositions as these a cloudy and high expansion glass which itis desired to avoid.

Glass B has gone into extensive commercial use in the manufacture ofbaking dishes, and chemical Ware, many thousands of which have beensold, and has been tested by the Bureau of Standards, who find itslinear expansivity to be .0000033; its true internal heat conductivityto be .0028; its density to be 2.246. Other tests show its true tensilestrength to be 16 kg. per sq.

mm.; its Youngs modulus to be 6530, giv

ing a true coeflicient of thermal endurance of 19. Its hardness, asdefined above,

endurance is about 10.

3 Having thus described our invention, What we claim,'and desire tosecure by Letters Patent is stated in the following clalms,

in certain of which the term acid is used as indicating the oxids ofaluminum and antimony 1. A glass containing silica, alumina, boric oxidand sodium oxid only, the silica being not under 70 per cent, and thealumina being not over 3 per cent. of the total, and thepercentage ofboric oxid to sodium oxid being not less than two to one.

2. A glass containing silica, alumina, boric oxid and sodium, oxid,without oxids of the second group of the periodic system, or thereducible oXids of lead or antimony, the silica being not under 70 percent, and the alumina being not over 3 per cent. of the total, and thepercentage of boric oxid to sodium oxid being not less than two to one.

3. A glass containing not under 70 per cent. and not over 90 per cent.silica and alumina, boric oxid and an alkali oxid, the boric oxid beingnotless than 60 per cent. or more than 70 per cent. of the combinedalumina, boric oxid and alkali oxid con- 5. A glass containing not under76 per cent. silica and .also contairiing boric oxid,

the boric oxid comprising not less than 60 ing boric oxid, the boricoxid comprising than 850 (3.; a co-efiicient of thermal en- .not lessthan 60 per ccnt..of ingredients other than silica.

7. A glass containing between 76 and 90 er cent. silica between 6 and 14per cent. oric oxid, and also containing sodium oxid and alumina. 1

8-. A glass containing silica, boric oxid and alkali, the boric oxid andalkali forming not less than 6 per cent. of the glass, the glass havinglinear co-eflicient of expansion less than .0000036.

9. A glass containing silica, boric oxid and alkali, the boric oxidandalkali forming not less than 6 per cent. of the glass, and the boricoxid being to the alkali in the ratio of at least two to one, the glasshaving a linear co-efficient of expansion of less than .0000036.

10.A glass containing silica, boric oxid and alkali without oxids of thesecond group of the periodic system, or the reduci-' cient-of expansionof less than .0000036 and a hardness not greater than 800 C. p

. 12. A transparent glass containing more than 79 per cent. silica andhaving a linear co-efiicient of expansion less than .000004, and ahardness not greater than 850. C.

' 13. A glass having a hardness not greater (nuance greater than andstability 0 or 0.002 g. or better per 100 sq. cm.

14. A glass having a hardness not greater than 850 0., a linearco-efficient of expansion of lessjthan .0000036, and thermal coefficientof endurance greater than six. 15. A glass having linear expansivityless than 0.000004, stability better than 0.002 grams per 100 sq. cm.and hardness not greater than 850 C 16. A glass containing silica andboric oxid and having linear expansivity less than 0.000004 andstability better than 0.002

grams per'100 sq'. cm.

17. A glass having hardness not greater than 820 C. and linearexpansivity less than the acid oxid contents except such as are due tosilica to thebasic oxid contents being at least two to one.

20. A lass containing at least 76 per cent. silica and containing atleast one other acid oxid and a basic oxid, the percentage ratio of theacid oxid contents except such as are due to silica to the basic oxidcontents being at least two to one.

21. A glass containing silica and not more than two other acidic oxids,one of which may be alumina and only one basic oxid; the molecular ratioof the acidic oxid contents, except such as are due to silica andalumina, to the basic oxid contents being at least two to one. .1

22. A glass containing at least two acidic constituents and only onebasic constituent,

and having linear expansivity l th 23. A glass containing silica and notmore than two other acidic constituents and only one basic oxidconstituent, and having linear expansivity less than .000004.

24. A glasscontaining between.76 per cent. and 85 per cent. silica, over9% of another acid oxid, and over 3% of a basic oxid.

- 25. A glass containing over 7 6 per cent.

silica and having linear expansivity less than 0.000004 and hardness notgreater than 820 0.

Intestimony whereof we names.

EUGENE C. SULLIVAN. WILLIAM C. TAYLOR.

have signed our 7

